The present invention relates to a semi-continuous process for making resinous star-block copolymers.
Highly branch block copolymers, sometimes called star-blocked copolymers, are old in the art of anionic polymerization. These star-block copolymers are prepared by first forming linear block polymers having active lithium atom on one end of the polymer chain. These active, linear polymer chains are then coupled by the addition of a polyfunctional compound having at least three reactive sites capable of reacting with the carbon to lithium bond on the polymer chains to add the polymer chain onto the functional groups of the compound.
Zelinski, U.S. Pat. No. 3,280,084, polymerized butadiene with butyllithium initiator to form B-Li blocks (where B is polybutadiene) which when coupled with 0.02 to 1 part by weight per 100 parts of monomers of divinylbenzene gave starblock copolymers having polydivinylbenzene nuclei and several identical arms of polybutadiene branching therefrom. The arms can also be either random or block copolymers of styrene and butadiene (from A-B-Li blocks, where A is polystyrene segment) where the diene is the major component.
Zelinski, U.S. Pat. No. 3,281,383, teaches similar star-block copolymers to those in U.S. Pat. No. 3,280,084, except that coupling agents such as polyepoxy compounds, polyacids, polyaldehydes, etc., are used.
Childers, U.S. Pat. No. 3,637,554, prepares rubbery starblock copolymers having nuclei formed from polyepoxides, polyisocyanates, polyimines, etc., and identical arms from B-Li and A-B-Li.
Kitchen et al, U.S. Pat. No. 3,639,517, teaches that star-block copolymer may be formed having different molecular weight arms attached to the same nucleus. These arms are formed by using multiple additions of styrene monomer and initiator to form A-Li; A'-Li; and A"-Li, where A, A' and A" are polystyrene blocks of different molecular weights, then by a single addition of butadiene, and finally coupling these arms to form star-block copolymers having bi-, tri and polymodal molecular weight distribution in the arms.
Fetters et al, U.S. Pat. No. 3,985,830, discloses a product having a nucleus of more than one molecule of m-divinyl-benzene and at least three polymeric arms, each being a block copolymer of conjugated diene and monovinyl aromatic monomers wherein said conjugated diene block is linked to said nucleus.
Fahrback et al, U.S. Pat. No. 4,086,298, discloses star-block copolymers having a mixture of arms wherein some are formed by first polymerizing styrene with alkyllithium to form A-Li blocks, and then adding a mixture of styrene and butadiene to form a graded copolymer represented by A-B.fwdarw.A', where the arrow represents a graded segment. Other arms are made up on only the butadiene-styrene graded copolymer segment.
Bi et al., U.S. Pat. No. 4,221,884, discloses star-block copolymers having bimodal distribution of molecular structure in the arms of the copolymer wherein the elastomeric segments comprise a random block followed by a polydiene block next to the star nucleus.
The above patents all suffer from the disadvantage of being lengthy batch processes which require cleaning out of the batch reactor after each run.